TWI735226B - Method for three-dimensionally determining an aerial image of a lithography mask - Google Patents
Method for three-dimensionally determining an aerial image of a lithography mask Download PDFInfo
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
- G03F1/82—Auxiliary processes, e.g. cleaning or inspecting
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70491—Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes
- G03F7/705—Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
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Abstract
Description
[相關申請案交互參照][Cross-reference related applications]
德國專利申請案DE 10 2019 206651.8的內容以引用方式併入本文中。The content of German
本發明係關於一種通過投影曝光設備的變形投影曝光成像光學單元,以三維方式確定作為成像結果的微影光罩的空照影像(aerial image)之方法。The present invention relates to a method for determining an aerial image of a lithography mask as an imaging result in a three-dimensional manner through a deformed projection exposure imaging optical unit of a projection exposure device.
從US 2017/0131528 A1 (平行文件WO 2016/012 425 A2)和從US 2017/0132782 A1中已知這樣的方法和計量系統。Such methods and metering systems are known from US 2017/0131528 A1 (parallel document WO 2016/012 425 A2) and from US 2017/0132782 A1.
本發明的目的是通過使用包括具有同構成像比例尺的測量成像光學單元之一計量系統,來改善要確定藉由一變形投影曝光成像光學單元成像的一微影光罩之3D空照影像準確性。The purpose of the present invention is to improve the accuracy of the 3D aerial image of a lithography mask imaged by an anamorphic projection exposure imaging optical unit by using a measurement system including a measuring imaging optical unit with the same constituent image scale. .
根據本發明藉由具備請求項1內指定特徵的一空照影像確定方法來達成此目的。According to the present invention, this objective is achieved by an aerial image determination method with the specified characteristics in
根據本發明,已經認識到可改善投影曝光成像光學單元的散焦空照影像之近似值,這對於完成三維空照影像是必要的,即通過使用至少一個修正項,藉助於計量系統內測量光學單元的可移動及/或可變形測量光學單元部件之目標不對準,捕捉與該成像光學單元的影像平面垂直之第三空照影像維度。該至少一個修正項包括照明設定的個別重建光譜。該至少一個修正項一方面考慮該投射曝光設備內成像光學單元的散焦依賴性與另一方面考慮該計量系統的測量光學單元之失準依賴性之間差異的照明設定影響。就使用兩個修正項而言,其較佳以不同符號併入初始測量步驟中獲得的測量結果之修正中。由於兩個修正項合併相同的重建光譜,因此在光譜重建過程中出現的錯誤隨後由於使用兩個修正項而相互抵消。According to the present invention, it has been recognized that the approximate value of the defocused aerial image of the projection exposure imaging optical unit can be improved, which is necessary for the completion of the three-dimensional aerial image, that is, by using at least one correction item, by means of the measurement optical unit in the measurement system The target of the movable and/or deformable measuring optical unit component is not aligned, and the third aerial image dimension perpendicular to the image plane of the imaging optical unit is captured. The at least one correction term includes individual reconstructed spectra of lighting settings. The at least one correction term takes into account the influence of the illumination setting of the difference between the defocus dependence of the imaging optical unit in the projection exposure device on the one hand and the misalignment dependence of the measurement optical unit of the metrology system on the other hand. As far as the two correction terms are used, they are preferably incorporated into the correction of the measurement result obtained in the initial measurement step with different symbols. Since the two correction terms merge the same reconstructed spectrum, the errors in the spectral reconstruction process are subsequently cancelled out due to the use of the two correction terms.
運用計量系統的同構測量成像光學單元,使得可藉助該確定方法,非常精確地確定由該變形投影曝光成像光學單元成像的該微影光罩之該3D空照影像。這可用於最佳化該微影光罩上的原始結構,以便在半導體組件(特別是記憶體晶片)的生產期間,改善其成像性能。因此並不必須使用一變形測量成像光學單元。此外,在通過測量成像光學單元進行的測量期間,垂直於場平面的場移位也不是必需的。Using the isomorphic measurement imaging optical unit of the metrology system makes it possible to determine the 3D aerial image of the lithography mask imaged by the deformed projection exposure imaging optical unit very accurately with the help of the determination method. This can be used to optimize the original structure on the lithography mask to improve its imaging performance during the production of semiconductor components (especially memory chips). Therefore, it is not necessary to use a deformation measuring imaging optical unit. In addition, during the measurement performed by the measurement imaging optical unit, the field shift perpendicular to the field plane is not necessary.
就如請求項2之重建而言,考慮到最小化所測量的和所模擬的成像光強度間之差異,就產生改善的光譜重建品質。這接著改善該方法的修正步驟中的測量結果修正。As far as the reconstruction as in
如請求項3之多個可移位及/或可變形的測量光學單元組件,用於產生該測量光學單元的該目標失準,以在每種情況下預定義不同的散焦值,而增加可用的自由度數量,從而使一方面由該投影曝光成像光學單元所成像而產生的該波前,與另一方面由該測量成像光學單元所成像旨在近似於該波前而產生的該波前間之差異最小化。相應可移位及/或可變形的測量光學單元組件的移位及/或變形對波前的影響較佳彼此線性獨立。因此,可有利地保持一方面在該投影曝光成像光學單元的波前與另一方面在該測量成像光學單元的波前之間在初始測量步驟中要最小化之差異為小。因此,該投影曝光成像光學單元的不同散焦值可由該測量光學單元完美模擬。該測量成像光學單元可恰好包括一個可移位及/或可變形的測量光學單元組件、可恰好包括兩個可移位及/或可變形的測量光學單元組件,或者可包括兩個以上的可移位及/或可變形的測量光學單元組件,例如三個、四個、五個或甚至更多個可移位及/或可變形的測量光學單元組件,用於測量成像光學單元的目標失準,以模擬投影成像光學單元的相應散焦值。For example, a plurality of displaceable and/or deformable measuring optical unit components of
如請求項4之照明設定光瞳之細分提高光譜重建的精度。該細分考慮以下物理事實:對於實際使用的微影光罩,也稱為霍普金斯近似的方法,根據該方法,照明方向的偏移僅導致光罩光譜的偏移,這僅對該照明方向內的小變化構成良好的近似。在下文中,這也稱為「局部霍普金斯近似」。For example, the subdivision of the illumination setting pupil of the
如請求項5之光譜重建提高光譜確認的精度。Such as request 5 spectral reconstruction to improve the accuracy of spectral confirmation.
如請求項6之空照影像確定方法,即使在散焦值相對較高的情況下,其也可生成3D空照影像資料,這對於預測投影曝光操作的穩定性相當有利。空拍影像確定方法所涵蓋的散焦值範圍可能會偏離理想焦點位置20 nm以上、30 nm以上、50 nm以上或100 nm以上。For example, the aerial image determination method of
如請求項7之繞射光譜測量使得例如能夠與重建光譜進行比較,這可以使一或多個修正項的確定更加準確。The diffraction spectrum measurement of
如請求項8之相位檢索演算法與繞射光譜的測量有關。精通技術人士可在US 2017/0132782 A1中找到有關此類演算法的資訊。For example, the phase retrieval algorithm of claim 8 is related to the measurement of diffraction spectrum. Technically savvy people can find information about this type of algorithm in US 2017/0132782 A1.
如請求項9之計量系統的優點對應於上面已經參考3D空照影像確定方法所解釋的優點。計量系統可測量用於投影曝光而提供的微影光罩,以產生具有極高結構解析度的半導體組件,該結構解析度例如優於30 nm,特別是可優於10 nm。The advantages of the metering system as in
圖1在與子午線截面相對應的截面圖中顯示在包括一變形投影曝光成像光學單元3的投影曝光設備2中EUV照明光或成像光1之光束路徑,該投影曝光設備由圖1中的方框示意呈現。照明光1在投射曝光設備2的照明系統4中產生,該照明系統同樣以方框示意性例示。照明系統4包括一EUV光源和一照明光學單元,兩者均未更詳細顯示。光源可以是雷射電漿源(LPP;雷射產生的電漿)或放電源(DPP;放電產生的電漿)。原則上,也可使用同步加速器型光源,例如自由電子雷射(FEL)。照明光1的使用波長可在介於5 nm與30 nm之間的範圍內。原則上,在投影曝光設備2的變型情況下,也可將光源用於其他一些使用的光波長,例如用於193 nm的使用波長。Figure 1 shows the beam path of EUV illumination light or
照明光1在照明系統4的照明光學單元中調節,如此提供該照明的特定照明設定,也就是特定照明角度分佈。該照明設定對應於該照明系統4中該照明光學單元的照明光瞳內照明光1之特定強度分佈。The
為了幫助呈現位置關係,此後都使用笛卡爾xyz座標系統。在圖1內,該x軸垂直於該圖式平面並往外延伸。y軸朝向圖1的右邊。z軸朝向圖1的上方。In order to help present the positional relationship, the Cartesian xyz coordinate system is used since then. In Fig. 1, the x-axis is perpendicular to the plane of the drawing and extends outward. The y-axis is toward the right of Figure 1. The z-axis faces the upper side of Figure 1.
照明光1照亮投影曝光設備2的物平面6之物場5。在物平面6中佈置有一微影光罩7,也稱為倍縮光罩(reticle)。在平行於xy平面延伸的物平面6上方,於圖1中示意性顯示微影光罩7的結構截面。該結構截面例示為位於圖1中的圖式平面內。微影光罩7的實際佈置垂直於物平面6中圖1內的圖式平面。The
如圖1中示意性所示,照明光1從微影光罩7反射,並在入射光瞳平面9中進入成像光學單元3的入射光瞳8。成像光學單元3的使用入射光瞳8具有橢圓形邊界。As schematically shown in FIG. 1, the
在成像光學單元3之內,該照明或成像光1在入射光瞳平面9與出射光瞳平面10之間傳播。成像光學單元3的圓形出射光瞳11位於出射光瞳平面10內。成像光學單元3變形,並且從橢圓形入射光瞳8產生圓形出射光瞳11。Within the imaging
成像光學單元3將物場5成像到投影曝光設備2的像平面13內之像場12中。圖1示意性顯示在像平面13下方的一成像光強度分佈IScanner
,其在沿z方向與像平面13間隔值zw
的平面中測量,也就是在散焦值zw
的情況下之成像光強度。在通過投影曝光成像光學單元3進行成像的情況下,這種測量的成像光強度分佈IScanner
的另一範例顯示於圖3中。The imaging
在物平面6與像平面13之間,特別是由於成像光學單元3的組件所導致之波前像差φ,該波前像差示意性顯示為實際波前值與圖1內期望波前值(散焦= 0)的散焦偏差。Between the
在像平面13周圍不同z值處的成像光強度IScanner
(xy)也稱為投影曝光設備2的3D空照影像。投影曝光裝置2具體實施為一掃描器。在投影曝光期間,一方面微影光罩7與另一方面佈置在像平面13中的晶圓彼此同步掃描。結果,微影光罩7上的結構轉移至該晶圓。 The imaging light intensity I Scanner (xy) at different z values around the
圖2顯示用於測量微影光罩7的一計量系統14。計量系統14用於以三維方式確定微影光罩7的空照影像,近似於投影曝光設備2的實際空照影像IScanner
(xyz)。FIG. 2 shows a
上面已參考圖1解釋的組件和功能在圖2中具有相同的參考符號,並且將不再詳細討論。The components and functions explained above with reference to FIG. 1 have the same reference symbols in FIG. 2 and will not be discussed in detail.
與投影曝光設備2的變形成像光學單元3相反,計量系統14的測量成像光學單元15具體實施為一同構光學單元,也就是說,具體實施為具有一同構成像比例的一光學單元。在這種情況下,除了整體成像比例之外,在形狀方面,測量入射光瞳16忠實轉換成測量出射光瞳17。計量系統14在入射光瞳平面9中具有橢圓形孔徑光欄16a。從WO 2016/012 426 A1中已知計量系統中的這種橢圓形孔徑光欄16a之具體實施例。該橢圓形孔徑光欄16a產生測量成像光學單元15的橢圓形測量入射光瞳16。在這種情況下,孔徑光欄16a的內邊界預定義測量入射光瞳16的外輪廓。此橢圓形測量入射光瞳16轉換成橢圓形測量出射光瞳17。橢圓形測量入射光瞳16的長寬比可與投影曝光設備2中成像光學單元3的橢圓形入射光瞳8之長寬比完全相同。關於該計量系統,也可參考WO 2016/012 425 A2。In contrast to the anamorphic imaging
測量成像光學單元15具有至少一個可移位及/或可變形的測量光學單元組件。這種測量光學單元組件在圖2中的Mi
處示意性例示為一反射鏡。測量成像光學單元15可以包括多個反射鏡M1、M2…,並且可包括這種測量光學單元組件的對應的多個Mi
、Mi+1
。The measuring imaging
可移位及/或可變形的測量光學單元組件Mi
的可移位性及/或可操作性在圖2中由操縱桿18示意性示出。操縱的自由度在圖2中用雙向箭頭α表示。根據可移位及/或可變形的測量光學單元組件Mi
之分別設定未對準,波前像差φ(α)結果(以與圖1類似的方式)也在圖2中示意性示出)。The displaceability and/or operability of the displaceable and/or deformable measuring optical unit assembly M i is schematically shown by the
在計量系統14的測量平面19中佈置有空間分辨偵測裝置20,其可為CCD相機,該測量平面構成該測量成像光學單元的像平面。A spatial
以類似於圖1中的方式,圖2在測量平面19下方顯示根據可移位及/或可變形測量光學單元組件Mi 中各自未對準的強度測量結果Imeasured (x, y,)。圖4中顯示這種強度測量Imeasured 的另一範例。In a manner similar to that in FIG. 1, FIG. 2 shows the misalignment of the displaceable and/or deformable measurement optical unit components M i below the measurement plane 19 I measured (x, y, ). Another example of this intensity measurement I measured is shown in Figure 4.
從測量平面19內計量系統14的測量結果可確定投影曝光設備2的空照影像,這將在下面詳細說明。The aerial image of the
這涉及首先在散焦值zr
具有Rayleigh單元λ/NA2 wafer
的絕對值之情況下,計算投影曝光設備2的成像光學單元3之波前像差φ。在這種情況下,λ是照明光1的波長,並且NAwafer
是投影曝光設備2的成像光學單元3之像側數值孔徑。此波前像差確定用於波向量k。This involves first calculating the wavefront aberration φ of the imaging
然後將此波前像差寫入當成Zernike函數的展開,並且這次在像平面13中產生掃描器波前像差的Zernike展開之目標Zernike係數。然後尋求該操縱器位置Δα或操縱器位置Δαi的組合,這產生測量成像光學單元15的波前像差φ,波前像差φ的Zernike展開產生最接近係數的Zernike係數。在該操縱器位置或這組操縱器位置的情況下,藉助於計量系統14,然後在偵測裝置20的幫助之下記錄微影光罩7的影像。Then write this wavefront aberration as the expansion of the Zernike function, and this time produce the target Zernike coefficient of the Zernike expansion of the scanner wavefront aberration in the
然後針對不同的散焦值重複此方法,該方法首先涉及在投影曝光設備2的成像光學單元3之這種散焦情況下確定該波前像差,然後確定該測量成像光學單元的哪一個該組操作Δα和該組Zernike係數能夠最佳模擬此散焦波前像差。This method is then repeated for different defocus values. The method first involves determining the wavefront aberration under such defocusing conditions of the imaging
例如,可以針對Rayleigh單元的n = -2、-1.5、-1、-0.5、0、0.5、1、1.5和2之倍數完成此操作。圖5顯示在測量平面19中強度測量的相應結果。在這些散焦值每一者的情況下,因此實行操縱器設定,使得該測量成像光學單元的相關波前像差之Zernike係數分別以最小誤差與該投影曝光設備2中該成像光學單元的該波前像差之Zernike係數匹配。For example, this can be done for multiples of n = -2, -1.5, -1, -0.5, 0, 0.5, 1, 1.5, and 2 for Rayleigh elements. Figure 5 shows the intensity measurement in the
因此,在用於微影光罩7的空照影像Iscanner
中三維確定方法之初始測量步驟中,測量3D空照影像作為測量強度來當成散焦值zw
的函數,也就是說,藉助於具有測量光學單元15,而該單元具有一同構數值孔徑和至少一個可移位測量光學單元組件Mi
的計量系統14,多個散焦測量平面分別對應於散焦值(zw
)。使用橢圓形孔徑光欄16a對入射光瞳16完成此測量,其中該光瞳在測量成像光學單元15中的長寬比與1之差大於10%。此外,在分別指派給該散焦值的測量成像光學單元15之目標未對準影響下,完成此測量。如上所述,該目標未對準導致藉助於投影曝光設備2的成像光學單元3對該微影光罩成像而產生的波前φ(),與藉助於具有以目標方式移位的一測量光學單元組件Mi
之測量成像光學單元15對微影光罩7成像而產生的波前φ()間之差異最小化。Therefore, in the initial measurement step of the three-dimensional determination method in the aerial image I scanner used for the
在操縱器位置對應於Rayleigh單元的不同倍數(n = -2、…n = 2)之情況下,由計量系統14測量一系列該等空照影像,以及相應的Zernike係數(其產生在相關聯的波前像差之誤差最小匹配時),然後將用於測量並在投影曝光期間對應至所使用的該照明設定的照明設定用於重建光罩光譜。In the case where the position of the manipulator corresponds to different multiples of the Rayleigh unit (n = -2,...n = 2), the
在這種情況下,使用文獻中稱為霍普金斯近似的近似。此近似基於這樣的假設:除了偏移之外,兩不同照明方向的相應光罩光譜是相同的。在這種情況下,霍普金斯近似僅局部應用,也就是說對於彼此接近的照明方向。這考慮到以下事實:對於彼此遠離的照明方向,由於微影光罩的三維結構所產生之陰影導致不同的照明光譜。有關霍普金斯近似的詳細資訊,例如在Artech House於2013年在A. Taflove編輯的參考書「Advances in FDTD Computational Electrodynamics」的第15章中進行了說明。In this case, an approximation called the Hopkins approximation in the literature is used. This approximation is based on the assumption that, except for the offset, the corresponding mask spectra of the two different illumination directions are the same. In this case, the Hopkins approximation is only applied locally, that is to say for illumination directions that are close to each other. This takes into account the fact that for the illumination directions that are far away from each other, the shadows produced by the three-dimensional structure of the lithography mask result in different illumination spectra. Detailed information about the Hopkins approximation is described in
圖6在左側顯示一範例照明設定,其例示為照明系統4的照明光瞳平面21 (參見圖1和2)中之強度分佈。該照明設定具體實施為一四極照明設定,其中在圖6中,各個照明極點σ作為光瞳坐標qx
,qy
的函數在左側用σ1至σ4表示。這些極點σ1至σ4中的每一個都代表照明設定的光瞳部分。根據局部霍普金斯近似,可根據波向量為這些部分σ1到σ4分配傅立葉轉換F1
到F4
。根據局部霍普金斯近似,在相應極點σi
內的照明角度變化導致微影光罩7的相應繞射光譜Fi之頻率位移。Fig. 6 shows an example illumination setting on the left, which is illustrated as the intensity distribution in the
使用這種非局部霍普金斯近似,可將整個空照影像寫入為相對於四個照明極點的四個光譜之疊加,如下所示: Using this non-local Hopkins approximation, the entire aerial image can be written as a superposition of the four spectra relative to the four illumination poles, as shown below:
在此案例中:是分為N個部分的照明設定,也就是說,在當前情況下分為四個部分;是投影光學單元的振幅變跡函數(在可用數值孔徑內為1,在之外為0);是成像光學單元的波前像差,描述為具有Zernike係數的Zernike函數之展開;是上面解釋的微影光罩,分配給每個光瞳部分σi (i = 1 .... N)。In this case: It is a lighting setting divided into N parts, that is, it is divided into four parts under the current situation; Is the amplitude apodization function of the projection optical unit (1 within the available numerical aperture, 0 outside); Is the wavefront aberration of the imaging optical unit, described as the expansion of the Zernike function with Zernike coefficient ; It is the lithography mask explained above, which is assigned to each pupil part σ i (i = 1 .... N).
在根據圖5進行一系列空照影像測量以及相關Zernike係數的光罩光譜F1 … N 之重建中,則採用以下程序:In accordance with Figure 5, a series of aerial imagery measurements and related Zernike coefficients In the reconstruction of the mask spectrum F 1 … N , the following procedure is used:
針對照明設定的每個部分σ1重建光譜Fi。為此,首先將初始光譜或原始光譜Fi當成臨時候選值,該光譜例如通過相應的空照影像測量之傅立葉轉換原地生成。此後,從這些原始光譜Fi計算空照影像,在每種情況下使用在初始測量步驟中針對各個空照影像測量所確定的Zernike係數。然後,對於所有光瞳部分,也就是說,例如對於四個照明極點,確定實際空照影像測量值與模擬值之間的差Δ: The spectrum Fi is reconstructed for each part σ1 of the lighting setting. To this end, firstly, the initial spectrum or the original spectrum Fi is regarded as a temporary candidate value, and the spectrum is generated in situ, for example, by the Fourier transform of the corresponding aerial image measurement. Thereafter, the aerial image is calculated from these raw spectra Fi, using in each case the Zernike coefficients determined for each aerial image measurement in the initial measurement step. Then, for all pupil parts, that is, for example, for the four illumination poles, determine the difference Δ between the actual aerial image measurement value and the simulated value:
然後,在每種情況下,原始光譜Fi都進行反覆匹配,以使差異Δ最小,並且可選地對差異計算進行多次反覆。Then, in each case, the original spectrum Fi is iteratively matched to minimize the difference Δ, and the difference calculation is optionally repeated multiple times.
總體上,因此將光譜Fi重建為成像光1的場分別經傅立葉轉換成為微影光罩7中照明的照明設定內光瞳的特定部分σi
。該重建合併由測量光學單元15使用該可移位測量光學單元組件Mi
的該目標失準所測量的一成像光強度,與包括分別用於個別光譜的臨時候選值的一成像光強度之模擬間之差Δ。In general, therefore, the spectrum Fi is reconstructed into the field of the
一旦要重建的光譜Fi之反覆近似不再導致該值Δ的改善,就存在重構的光譜Fi,然後可根據該重建光譜Fi計算兩修正項。Once the repeated approximation of the spectrum Fi to be reconstructed no longer leads to an improvement in the value Δ, there is a reconstructed spectrum Fi, and then two correction terms can be calculated based on the reconstructed spectrum Fi.
在這種情況下,第一修正項是在相關散焦值zw
的情況下計算出之3D空照影像,該值通過利用包含重建光譜Fi的投影曝光設備2之變形投影曝光成像光學單元3的成像模擬而生成。In this case, the first amendment It is calculated in a case where the correlation value z w defocused aerial images of 3D, the value is generated by using the projection exposure apparatus comprising an analog reconstruction of the spectral
第二修正項是在相關散焦值zw
的情況下計算出之3D空照影像,該值通過利用包含重建光譜Fi的測量成像光學單元15之成像模擬而生成。The second correction term is the 3D aerial image calculated with the relevant defocus value z w This value is generated by imaging simulation using the measurement imaging
根據初始測量步驟的結果和兩修正項,可根據以下表達式確定變形投影曝光成像光學單元3的空照影像Iscanner
: According to the results of the initial measurement steps And two correction terms, the aerial image I scanner of the deformed projection exposure imaging
顯然,由於模擬或重建誤差在兩修正項中均以不同的符號出現,因此相互抵消。Obviously, since the simulation or reconstruction errors appear with different signs in the two correction terms, they cancel each other out.
圖7例示性顯示根據以上公式在計算3D空照影像Iscanner
時併入的不同項。在左上角,仍在計算之前,由變形投影成像光學單元3引起的實際波前像差情況下的搜尋空照影像用問號表示。右上角則顯示根據初始測量步驟得出的空照影像。左下角例示基於投影成像光學單元3的模擬結果之第一修正項,而右下角則例示第二修正項,也就是說,基於測量光學單元的模擬之該已計算空照影像。Fig. 7 exemplarily shows the different items incorporated in the calculation of the 3D aerial image I scanner according to the above formula. In the upper left corner, still before the calculation, the searched aerial image under the actual wavefront aberration caused by the deformed projection imaging
通過在US 2017/0132782 A1中所描述方法測量的繞射光譜也可用於確定至少一項修正項。The diffraction spectrum measured by the method described in US 2017/0132782 A1 can also be used to determine at least one correction term.
1:成像光
2:投影曝光設備
3:變形投影曝光成像光學單元
4:照明系統
5:物場
6:物平面
7:微影光罩
8:入射光瞳
9:入射光瞳平面
10:出射光瞳平面
11:圓形出射光瞳
12:像場
13:像平面
14:計量系統
15:測量成像光學單元
16:測量入射光瞳
16a:橢圓形孔徑光欄
17:測量出射光瞳
18:操縱桿
19:測量平面
20:空間分辨偵測裝置
21:照明光瞳平面
1: imaging light
2: Projection exposure equipment
3: Deformation projection exposure imaging optical unit
4: lighting system
5: Object field
6: Object plane
7: lithography mask
8: entrance pupil
9: Entrance pupil plane
10: Exit pupil plane
11: Round exit pupil
12: image field
13: Image plane
14: Metering system
15: Measuring imaging optical unit
16: measure the
下面將參考圖式來更詳細解釋本發明的示範具體實施例。在圖式中:Hereinafter, exemplary embodiments of the present invention will be explained in more detail with reference to the drawings. In the schema:
圖1示意性顯示用於EUV微影的投影曝光設備,包含用於成像一微影光罩的一變形投影曝光成像光學單元;Figure 1 schematically shows a projection exposure device for EUV lithography, including a deformed projection exposure imaging optical unit for imaging a lithography mask;
圖2示意性顯示用於確定該微影光罩的一空照影像之計量系統,其包括具有一同構成像比例的一測量成像光學單元;具有不同於1的長寬比之孔徑光欄;以及至少一個可移位的測量光學單元組件;Fig. 2 schematically shows a measurement system for determining an aerial image of the lithography mask, which includes a measuring imaging optical unit having an image ratio together; an aperture stop having an aspect ratio different from 1; and at least A displaceable measuring optical unit assembly;
圖3通過範例顯示在特定散焦值的情況下,藉助於根據圖1的投影曝光設備在該微影光罩成像期間,一影像平面中成像光的強度分佈,也就是說一測量平面與該影像平面的理想焦點位置間之偏差;Fig. 3 shows by way of example the intensity distribution of imaging light in an image plane during the imaging of the lithography mask by means of the projection exposure device according to Fig. 1 in the case of a specific defocus value, that is to say, a measurement plane and the The deviation between the ideal focus position of the image plane;
圖4顯示由根據圖2的該計量系統測量的一成像光強度,其中將該可移位測量光學單元組件設為藉助於該測量成像光學單元的目標失準,使得與根據圖3中該散焦相對應的散焦值被近似;Fig. 4 shows an imaging light intensity measured by the metering system according to Fig. 2, in which the displaceable measuring optical unit assembly is set to be misaligned with the target by means of the measuring imaging optical unit, so that it differs from the dispersion according to Fig. 3 The defocus value corresponding to the focus is approximated;
圖5顯示在倍縮光罩(reticle)成像期間於該計量系統影像平面中的成像光強度測量結果之序列,其中在每種情況下可移位測量光學單元組件的移位位置不同,對應於不同的散焦值;Figure 5 shows the sequence of the imaging light intensity measurement results in the image plane of the metrology system during the imaging of the reticle, in which the displacement position of the displaceable measuring optical unit assembly is different in each case, corresponding to Different defocus values;
圖6示意性顯示使用光譜確定空照影像的過程,該光譜分別表示該成像光場到該微影光罩照明的照明設定之特定光瞳區段之傅立葉轉換,其中此光譜確定過程以局部霍普金斯近似的方式執行;及Fig. 6 schematically shows the process of determining an aerial image using a spectrum, which respectively represents the Fourier transformation of the imaging light field to the specific pupil section of the illumination setting of the lithography mask illumination, wherein this spectrum determination process is based on the local Huo Pukins executes in an approximate manner; and
圖7顯示空照影像確定中的各個貢獻,即右上角為該計量系統的測量光學單元之已測得空照影像,左下角為該已計算空照影像的一修正項,其藉由含根據圖6重建光譜的該變形投影曝光成像光學單元通過成像模擬所獲得,並且右下角為已計算空照影像形式的另一個修正項,其藉由含該光譜的該計量系統之該測量光學單元通過成像模擬來產生,其中在每一情況下分別將相同的散焦值分配給不同的空照影像。Figure 7 shows the various contributions in the determination of the aerial image, that is, the upper right corner is the measured aerial image of the measuring optical unit of the measurement system, and the lower left corner is a correction term for the calculated aerial image. The deformed projection exposure imaging optical unit of the reconstructed spectrum of FIG. 6 is obtained by imaging simulation, and the lower right corner is another correction item of the calculated aerial image form, which is passed by the measuring optical unit of the measurement system containing the spectrum It is generated by imaging simulation, in which the same defocus value is assigned to different aerial images in each case.
1:成像光 1: imaging light
4:照明系統 4: lighting system
5:物場 5: Object field
6:物平面 6: Object plane
7:微影光罩 7: lithography mask
9:入射光瞳平面 9: Entrance pupil plane
10:出射光瞳平面 10: Exit pupil plane
14:計量系統 14: Metering system
15:測量成像光學單元 15: Measuring imaging optical unit
16:測量入射光瞳 16: measure the entrance pupil
16a:橢圓形孔徑光欄 16a: Oval aperture diaphragm
17:測量出射光瞳 17: Measure the exit pupil
18:操縱桿 18: Joystick
19:測量平面 19: Measuring plane
20:空間分辨偵測裝置 20: Spatial resolution detection device
21:照明光瞳平面 21: Illumination pupil plane
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